This invention relates to derivatives of melamine and other substituted melamine s-triazines, and to polyurethanes prepared therefrom.
Melamine and certain of its derivatives are known to be useful as flame retardant additives in polymeric materials, particularly in polyisocyanate-based polymeric foams. For example, the addition of melamine itself as a flame retardant additive is taught in U.S. Pat. No. 4,745,133, and GB Patent Nos. 2,177,405, 2,177,405 and 2,163,762. In addition, various derivatives of melamine, such as hydroxyalkylated melamines and melamine-formaldehyde resins, have also been incorporated into polyisocyanate-based polymers for various reasons, including imparting flame retardancy.
Unfortunately, the use of melamine and certain of its derivatives as additives increase the cost of the foam, and usually create problems in the processing or properties of the polymer, or both. This is a particular problem with melamine and its derivatives, as rather substantial amounts thereof are required to provide effective flame retardancy. Hydroxyalkylmelamine, for example, is high melting and is difficult to process in making polyurethanes. Melamine-formaldehyde resins are not stable, and tend to polymerize on standing. For such reasons, it is desired to reduce the level of flame retarding additives, instead preparing polymers using isocyanate-reactive materials which themselves impart flame retardant characteristics to the polymer. It would be especially desirable to provide an isocyanate-reactive material which can be reacted with a polyisocyanate to form a polymer having desirable physical properties and inherent flame retardant characteristics.